The present invention is directed to a device for electrodepositing of aluminum from an aprotic, oxygen-free and water-free aluminum-organic alectrolyte. The device comprises an electroplating tank for receiving a liquid and an anode plate and having a hood forming a protective chamber over the surfaces of the liquid and being closed to the outside with the protective chamber being filled with a protective atmosphere, an arrangement for conveying workpiece holders in the protective chamber for introduction into a support rack for electrically contacting and holding the workpiece holder while disposed in the liquid of the tank, and a pair of lock arrangements each including an antechamber, a liquid lock and a principal chamber, which is connected to the protective chamber through closable openings with one lock arrangement being a discharging lock and the other being a charging lock.
A device for electrodepositing of aluminum from an aprotic, oxygen-free, water-free aluminum-organic electrolyte, which device has a lock system with a liquid lock for introduction and removal of the goods to be electroplated is disclosed in U.S. Pat. No. 4,265,726 which was based on German OS No. 2,901,586. In the device of this patent, the goods, which are to be electroplated, are accommodated on workpiece supports or workpiece holders which can be introduced with the assistance of an endless conveyor belt from an antechamber floodable with an inert gas through a liquid lock and into an electroplating bath or vat. After the electroplating has been accomplished, the holder is again transferred in the reverse direction with the assistance of the same conveyor belts. A disadvantage of this known device is that a rather considerable amount of the electrolyte is entrained from the electrolyte vat or bath into the liquid lock. Due to this continuing contamination of the liquid forming the liquid lock with the electrolyte, an unavoidable reaction with traces of air or moisture in the antechamber flooded with the inert gas will occur. These reaction products cannot be prevented from being deposited at unfavorable locations on the workpice, which is to be aluminized and which was previously cleaned, as the workpiece is transported into the electroplating space through the liquid lock which acts both as a charging and discharging lock. Therefore, these parts can no longer be coated with technically usable aluminum coatings.
In an earlier patent application, U.S. Ser. No. 318,812, filed Nov. 6, 1981 which issued as U.S. Pat. No. 4,363,712 and is based on German patent application No. 3,044,975, a charging lock is provided for introducing of the workpiece holders or carriers and also a discharging lock is provided for allowing the removal of the workpiece holders containing the plated workpiece. In order to increase the amount of throughput, it is further proposed that the known electroplating tank be employed with an annular closed electroplating vat in which a multitude of workpiece holders can be simultaneously accommodated. For this reason, the electroplating tank contains a support device for the workpiece holders which both contacts and holds the workpiece holders. This device is rotatable around a vertical axis of rotation and has brackets for receiving each of the workpiece holders so that they are moved in a circular arc or path in a substantially horizontal plane. As a result of the annular design of the electrolyte bath or vat, the workpiece holders can be moved through the electrolyte in a circular path and by so doing can be coated with aluminum at a higher current density. Moreover, as a result of the annular design of the electrolyte bath, the spatial separation of the charging and discharging of the workpiece holders through separate charging and discharging locks is made possible so that the individual brackets can be simultaneously loaded and emptied clockwise without sufficient interruptions. With the assistance of the known endless chain conveyors, the workpiece holders carrying the workpiece are introduced from a prelock, or antechamber, which is flooded with inert gas, through a U-shaped liquid lock into a principal chamber which is filled with inert gas and then are automatically transferred into the electroplating tank where the workpiece holder is received on the support device that has electrical contacts. After electroplating, the workpiece holders are automatically removed from the brackets of the support device with the assistance of an additional endless chain conveyor and are transferred through the liquid lock of the discharging lock into a prelock.
However, since the device of the copending application utilizes a closed, annularly shaped electroplating vat or bath, it is subjected to limits with regard to its size. For example, the size of the bath cannot be easily changed without substantial structural cost particularly for the rotatable support means which has the electrical contacts for the workpiece holders and for the structure of the bath.